4) completing the circuit of both sets of pins.4) completing the circuit of both sets of pins.
When the relay is energized, the coil shifts theWhen the relay is energized, the coil shifts the
switch, connecting pins (9 and 5) and pins (12 andswitch, connecting pins (9 and 5) and pins (12 and
8) completing the circuit of both sets of pins.8) completing the circuit of both sets of pins.
The most effective way to troubleshoot this typeThe most effective way to troubleshoot this type
relay is wirelay is with an ohmmeterth an ohmmeter. . This can be accom-This can be accom-
plished by removing the wires at relay socket ter-plished by removing the wires at relay socket ter-
minals (12, 8, and 4) and terminals (9, 5, and 1).minals (12, 8, and 4) and terminals (9, 5, and 1).
In a de-energized state, ensure that terminals (9In a de-energized state, ensure that terminals (9
and 1) and terminals (12 and 4) have continuityand 1) and terminals (12 and 4) have continuity
between them. between them. With an ohmmWith an ohmmetereter, check the, check the
resistance between terminals (9 and 1) and termi-resistance between terminals (9 and 1) and termi-
nals (1nals (12 and 2 and 4). 4). The ohmmThe ohmmeter shoueter should indicld indicate aate a
readreading of 0 - 40 ing of 0 - 40 ohmsohms. . EnerEnergize the regize the relay andlay and
check the resistance between terminals (9 and 5)check the resistance between terminals (9 and 5)
and termiand terminals (12 and 8)nals (12 and 8). . The ohmmetThe ohmmeter shoulder should
indiindicate a readicate a reading of 0 ng of 0 - 40 ohms. - 40 ohms. If thesIf these twoe two
checchecks are good, thks are good, the relay is gooe relay is good. d. If one ofIf one of
these checks fails and 12 VDC required at ter-these checks fails and 12 VDC required at ter-
88
55
44 11
99
1212
1414
1313
IllustIllustration 6-7. ration 6-7. DPDP, DT 15 amp Relay, DT 15 amp Relay
minal 14 was or was not present, or ground signalminal 14 was or was not present, or ground signal
at terminal 13 was or was not present, dependantat terminal 13 was or was not present, dependant
on the desired state of relay (energized or de-en-on the desired state of relay (energized or de-en-
ergized), the relay is bad and must be replaced.ergized), the relay is bad and must be replaced.
Double-Pole, Double-Throw Latching RelaysDouble-Pole, Double-Throw Latching Relays
(Illustration 6-8)(Illustration 6-8).. A relay is nothing more than anA relay is nothing more than an
electrielectrically contrcally controlled switcolled switch. h. This type of relay isThis type of relay is
showshown in a n in a resreset statet state. e. A latchiA latching relay has ang relay has a
power savipower saving feature. ng feature. It does not requirIt does not require the relaye the relay
coil to be energized at all times to maintain the setcoil to be energized at all times to maintain the set
state. state. The positiThe positive side of the relay cve side of the relay coil is pin 14oil is pin 14
while the negative side of the coil is pin 13 for thewhile the negative side of the coil is pin 13 for the
set state of the relset state of the relayay. . The internal rThe internal red flag of theed flag of the
relay will be visible in the small window, located atrelay will be visible in the small window, located at
the top of relay’s covthe top of relay’s coverer, indicating a set state. , indicating a set state. In aIn a
set state, pins (10 and 5) and pins (6 and 8) of theset state, pins (10 and 5) and pins (6 and 8) of the
relay will be closed and continuity exists betweenrelay will be closed and continuity exists between
each set of pins. each set of pins. In a reset state, tIn a reset state, the positive she positive sideide
of the relay coil is pin 12 while the negative side ofof the relay coil is pin 12 while the negative side of
the coithe coil is pin 9. l is pin 9. In a reset staIn a reset state, pinte, pins (10 and 1)s (10 and 1)
and pins (6 and 4) of the relay will be closed andand pins (6 and 4) of the relay will be closed and
continuitcontinuity exists by exists between each set of pinsetween each set of pins. . TheThe
internal red flag of the relay will not be visible ininternal red flag of the relay will not be visible in
the small window in the top of the relay’s cover,the small window in the top of the relay’s cover,
indicatiindicating a reset state. ng a reset state. A constant 12 VDC siA constant 12 VDC signalgnal
is not required to set or reset the latcis not required to set or reset the latching relayhing relay. . AA
momentary 12 VDC signal is required at either themomentary 12 VDC signal is required at either the
set or reset coil, depending on the desired state ofset or reset coil, depending on the desired state of
the relay, to set or reset the relay.the relay, to set or reset the relay.
The most effective way to troubleshoot this typeThe most effective way to troubleshoot this type
relay is wirelay is with an ohmmeterth an ohmmeter. . This can be accom-This can be accom-
plished by removing the wires at relay socket ter-plished by removing the wires at relay socket ter-
minminals (als (10, 1, and 5) and (6, 8, an10, 1, and 5) and (6, 8, and 4). d 4). Set theSet the
relrelay by applyay by applying 12 VDC to pin 14. ing 12 VDC to pin 14. In a set stateIn a set state
(the internal red flag is visible in the window),(the internal red flag is visible in the window),
ensure that terminals (10 and 5) and (6 and 8)ensure that terminals (10 and 5) and (6 and 8)
have continuihave continuity between them. ty between them. With an ohmmWith an ohmme-e-
ter, check the resistance between terminals (10ter, check the resistance between terminals (10
and 5) and then termand 5) and then terminalinals (6 and 8). s (6 and 8). The ohmThe ohmme-me-
ter should indicate a reading of 0 - 40 ohms.ter should indicate a reading of 0 - 40 ohms.
Reset the relay by applying 12 VDC to pin 12 (theReset the relay by applying 12 VDC to pin 12 (the
internal red flag should not be visible in the win-internal red flag should not be visible in the win-
dow). dow). Check the resiCheck the resistance between termstance between terminals (6inals (6
and 4) and then termand 4) and then terminalinals (10 and 1). s (10 and 1). The ohmThe ohm--
metmeter shouler should indicd indicate a readinate a reading of 0 g of 0 - 40 ohms. - 40 ohms. IfIf
these four cthese four checks arhecks are good, the relay e good, the relay is good. is good. IfIf
one of these checks fails and 12 VDC required atone of these checks fails and 12 VDC required at
terminals (14 or 12) was or was not present andterminals (14 or 12) was or was not present and
ground signal at terminals (13 or 9) was present,ground signal at terminals (13 or 9) was present,
dependant on the desired state of relay (set ordependant on the desired state of relay (set or
reset), the relay is bad and must be replaced.reset), the relay is bad and must be replaced.
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